Route A5 is the Anzac Highway from Adelaide City to Glenelg and a tiny portion of Greenhill Road. It is probably the second most historic road in Adelaide, behind Port Road. The route is dual carriageway for its entire length and is paralleled by the Adelaide-Glenelg Tram Line. The route was introduced in 1998 and was previously unnumbered.

Anzac Highway was named in 1938 and the reconstruction of the road to wide dual carriageways commenced that year. The reconstruction was completed in 1939 just prior to the onset of the World War 2. In 1957 the intersection with South Road was reconstructed and the first vehicle-actuated traffic signals were installed to improve traffic flow. In April 1959 Rolf Jensen, Superintending Engineer (Planning) of the Highways Department expressed the need for grade separations at major intersections along Anzac Highway to cater for future traffic growth but nothing eventuated. In October 1966 a new bridge across the railway lines at Keswick was opened to traffic, replacing a level crossing.

In May 2005 the South Australia Office For Instrastructure Development announced that in mid-2007 construction would commence on an underpass to carry South Road traffic beneath the Anzac Highway at Ashford. The underpass would cost $65 million and be completed in mid-2009.